1. Field of the Invention
The present invention relates to a thermoplastic resin composition. More particularly, it pertains to a thermoplastic resin composition which comprises at least two types of specific thermoplastic resins compounded with a novel copolymer having a formamide group and/or an amino group to enhance the compatibility among the aforesaid resins, which composition is excellent in all respects including surface impact strength, Izod impact strength and appearance.
2. Description of the Related Arts
Being generally excellent in both mechanical and thermal characteristics, an engineering plastics has recently been expanding to great proportions. Nevertheless, it is inferior to other general-purpose resins with respect to moldability, processability and production cost. In such circumstances, intensive research is concentrated on the settlement of the aforesaid problems and the development of concomitant characteristics by blending or alloying an engineering plastics with an olefinic resin or a styrenic resin each excellent in fluidity and advantageous in cost. A simple blending, however, leads to failure to compatibilize a plurality of different resins with each other, thereby causing such problems as remarkable deterioration of impact characteristics, liability to peeling or delamination and unfavorable appearance.
As the countermeasure against the above-mentioned problems, there has been carried out the development of compatilbilizers capable of improving the miscibility among the resins parallel to the improvement in the method of molding or processing. Examples of the technological method of improving miscibility include modification of resins, addition of a copolymer thereto, reaction with a reactive resin or a reactive reagent in an extruder and the combination of at least two of them.
Specifically, the modification of a constituent resin for polycarbonate is disclosed in Japanese Patent Application Laid-Open Nos. 157648/1980, 123251/1982, 201842/1983, 223742/1984 and 223749/1984. There is also proposed an intricate method of improvement with the combination of several means as disclosed in Japanese Patent Application Laid-Open Nos. 215714/1988, 215749 to 215753/1988 and 75543 to 75550/1989. In addition, there are disclosed the modification of polyamide or polyester with a modified polyolefin in Japanese Patent Application Publication No. 30954/1970 and a method of improving a resin composition comprising a styrenic copolymer containing maleic anhydride and a polyamide by means of glass fiber in Japanese Patent Application Laid-Open No. 62844/1981. Furthermore, an attempt is made to improve the delamination and Izod impact strength of the blend of polycarbonate, polyamide, polyester or polyether with a polyolefin by incorporating therein a polymer having an amino group and when necessary, a polyurethane in addition thereto in Japanese Patent Application Laid-Open No. 36248/1990.
The above-mentioned modification is intended to provide a new characteristic material by ingeniously combining the advantage of each of the components. However, in any of the aforesaid methods, the miscibility with each other is still insufficient, the above-described problems with regard to blending still remain unsolved and improvement can not be said to be sufficient on appearance and peeling on the surface of a resin product, especially on impact characteristics. For example, even if a resin as modified in the aforestated manner has a high Izod impact strength in impact characteristics evaluation which is usually made by means of Izod impact test, it is sometimes deteriorated in surface impact characteristics that is valuable in practice. In view of the above, the resin is required to be excellent in both Izod impact strength and surface impact characteristics in order that the resin may render itself really excellent in impact characteristics.
In the light of the above-described background, intensive research and investigation were made by the present inventors on the improvement of engineering plastics. As a result, it has been found by them that a thermoplastic resin composition excellent in impact characteristics, especially surface impact characteristics as well as appearance, minimized in coloration and free from delamination or peeling is obtained by melt kneading a thermoplastic resin such as engineering plastics and an olefinic polymer and/or a styrenic polymer with a novel copolymer having a formamide group and/or an amino group. The present invention has been accomplished on the basis of the above mentioned finding and information.